package com.ly.algorithm.offerpointer;

import java.util.Stack;

/**
 * @Classname Offer30
 * @Description
 *
 * 定义栈的数据结构，请在该类型中实现一个能够得到栈的最小元素的 min 函数在该栈中，调用 min、push 及 pop 的时间复杂度都是 O(1)。
 *
 *  
 *
 * 示例:
 *
 * MinStack minStack = new MinStack();
 * minStack.push(-2);
 * minStack.push(0);
 * minStack.push(-3);
 * minStack.min();   --> 返回 -3.
 * minStack.pop();
 * minStack.top();      --> 返回 0.
 * minStack.min();   --> 返回 -2.
 *
 *
 * @Date 2021/1/27 20:23
 * @Author 冷心影翼
 */
public class Offer30 {

    public static void main(String[] args) {

    }

}

class MinStack {


    private Stack<Integer> stack;
    private Stack<Integer> helpStack;

    public MinStack() {
        stack = new Stack<>();
        helpStack = new Stack<>();
    }

    public void push(int x) {
        stack.push(x);
        if(helpStack.isEmpty() || helpStack.peek()>= x) {
            helpStack.push(x);
        }
    }

    public void pop() {
        Integer pop = stack.pop();
        if(helpStack.peek().equals(pop)) {
            helpStack.pop();
        }
    }

    public int top() {
        return stack.peek();
    }

    public int min() {
        return helpStack.peek();
    }
}
